1. Field of the Invention
The present invention is related to tubular containers and, more particularly, to structural arrangement, method and apparatus utilized to produce laminated settable tubular packages which are substantially impermeable to volatile substances and atmospheric gases.
2. Description of the Prior Art
Various packages have been manufactured for use in containing a great many products such as toothpaste or the like which may be conveniently formed as tubular containers or packages. Various highly viscous products such as toothpaste may progressively be squeezed from such a package by foldably setting and rolling the package from the enclosed end toward the dispensing end. Conventional prior art packages utilized metal foil which, of necessity, was quite thick and expensive but had the desirable characteristic of being foldably settable. Such packages composed completely of metal foil were unsatisfactory in some situations where the settable material of the metal foil became brittle and cracked and caused leakage of contents from the package. Additionally, all-metal packages have been vulnerable to corrosion by their contents.
Various plastic packages have been used, but many of the all-plastic packages allow oxidation of products therein and allow volatile fluids of products to escape through the walls thereof and consequently an all-plastic package may now serve to contain some products over a considerable period of time. Furthermore, most plastic packages are not settable but remain resilient so that they cannot be conveniently folded and squeezed in such a manner as to progressively dispense material or products such as toothpaste or the like.
In accordance with prior art teachings, laminated tubular structures have been fabricated of sheets of material having a plurality of lamina wherein metal foil is bonded at its opposite sides to a polyolefin plastic material such as polyethylene or the like. These structures have a combination of desirable characteristics due to the fact that the intermediate metallic lamina serves as a barrier for volatile fluids and oxygen as well as to provide for a settable structure which may take a set when folded and hold the plastic lamina in folded condition such as is desirable in the progressive use of a toothpaste tube or the like which is typically progressively folded as the contents are dispensed therefrom. These structures also prevent corrosion of the metallic lamina since it is protected on both inner and outer sides by plastic material. Furthermore, the outermost polyolefin lamina is readily receptive to printing for the purpose of applying labels, trademarks, or other indicia on the outer sides of the hollow tubular wall structures.
Accordingly, the laminated tubular wall structures include many desirable characteristics and have therefore become quite versatile in the packaging of a great variety of products which may be oxidizable, corrosive to metal, or which may have volatile materials which tend to escape through plastics; and further, these laminated materials are readily mechanically settable and readily receptive to printing of indicia on the outer sides thereof.
Moreover, these laminated wall structures are relatively economical since a relatively small amount of metallic foil may be used with one or more thin economical lamina of polyethylene or the like on inner and outer sides of the metal foil.
The laminated structures including two lamina of plastic and one lamina of metal foil can be produced in sheet stock. Due to the relative thickness of the lamina and the requirement for accuracy relative thereto, it has been found most economical to produce such materials in sheet stock and then to form the sheet stock into tubular wall structures by butting the edges, or forming an overlapping seam, and then heating with or without the addition of other thermoplastic material to provide a fused seam.
The prior art includes numerous patents disclosing laminated tubular wall structures with metal foil barrier lamina and wherein several separate barrier structures are required in the shoulder and neck area of the prior art packages, and the production of such packages utilizing several barrier parts has been relatively complicated and costly.
When several metallic lamina barrier parts are utilized in the shoulder and neck area of a toothpaste tube or the like, it is difficult to produce such structures accurately and to bond the various parts together in such a manner as to prevent oxidation of the product and to prevent the escape of volatile materials from products contained in the packages.